Method for separating polybrominated diphenylether from waste electronic plastic

Abstract

The invention provides a method for separating polybrominated diphenylether from waste electronic plastic, comprising the following steps of: dissolving waste electronic plastic with an organic solvent to form a polymer solution; then refining the polymer solution through rough filtration and centrifugal filtration in sequence; contacting the filtered polymer solution with supercritical CO2 for extracting to reduce the solubility of polymer; precipitating the dissolved polymer in a solid state form; and separating out liquid phase and realizing the separation of the polymer and the polybrominated diphenylether. By adopting the separated polybrominated diphenylether from the waste electronic plastic, not only the concentration of polybrominated diphenylether in regenerated plastic can meetthe requirement on RoHS (Restriction of Hazardous Substance) instruction, but also solvent residue in the regenerated plastic can be reduced to safety level. In addition, by adopting the invention, the purity of regenerated plastic products can be improved, and favorable mechanical property is reserved, thereby realizing the high-efficiency and safe recycling of the waste electronic plastic.

Description

technical field [0001] The invention relates to the technical field of utilization of waste electronic plastics, in particular to a method for separating polybrominated diphenyl ethers from waste electronic plastics, which is suitable for recycling flame-retardant waste electronic plastics. Background technique [0002] The dismantling and recycling process of waste electronic and electrical equipment produces a large amount of plastic waste. Due to safety and fire prevention, these plastics are generally added with 5-20% brominated flame retardants, decabromodiphenyl ether, octabromodiphenyl ether is the main type. Polybrominated diphenyl ethers have been proven to be a class of persistent organic pollutants harmful to the environment, biology and human health. Therefore, the European Union issued the "Restriction on the Use of Certain Hazardous Components in Electrical and Electronic Equipment" (RoHS Directive) It clearly stipulates that since July 1, 2006, the mass fract...

AI Technical Summary

Problems solved by technology

However, there are the following problems in adopting this patent method to reclaim polybrominated diphenyl ether flame-retardant plastics: (1) decabromodiphenyl ether still has a solubility of 0.1 to 0.2wt% in these solvents at room temperature, and polybrominated diphenyl ethers below nonabromine The solubility of phenyl ether is larger. Due to the high boiling point and low volatility, most of the dissolved polybrominated diphenyl ethers cannot be removed with the solvent in the subsequent vacuum evaporation process, and the polybrominated diphenyl ethers in the regenerated resin thus obtained The concentration will still be higher than the ROHS standard

(2) In the stage of vacuum evaporation to remove solvent, as the concentration of solvent decreases, the viscosity of the system increases sharply, and the residual rate of solvent in the final recycled plastic is too high. If the selected solvent is toxic solvents such as toluene, tetrahydrofuran, and chloroform , too much residue will affect the safe use of the resin

If a natural low-toxic solvent such as limonene is used, the solvent residue problem will not affect the application of recycled plastic products, but due to the high price of such solvents, excessive solvent residue will greatly increase the recycling cost

[0008] It can be seen that the above-mentioned method for separating polybrominated diphenyl ethers from flame retardant plastics generally has one or more of the following deficiencies: (1) the residual solvent is too large, which affects the use and separation cost of the resin; (2) the cost of recycled resin products Although polybrominated diphenyl ether has been reduced, it still cannot meet the requirements of the RoHS directive; (3) due to the high viscosity of plastics and low mass transfer rate, the dissolution, extraction and separation time is long and the efficiency is low. (4) decabromodiphenyl ether in plastics The concentration of phenylene ether is high, and the solubility in general organic solvents and supercritical solvents is small, resulting in low separation efficiency and poor separation effect (5) Liquid-solid extraction separation of flame retardants in plastics is affected by the size of the contact interface, and the separation speed is slow

Due to the above deficiencies in the current technology, it cannot fully satisfy the regeneration of PBDE flame-retardant waste electronic and electrical plastics.